(a) Field of the Invention
The present invention relates to a novel one pot process for the preparation of an .alpha.-alkoxy acetic acid having the general formula EQU RO--CH.sub.2 COOH
or a salt thereof, wherein R can be straight or branched chain alkyl, substituted alkyl, cycloalkyl which may optionally be substituted, cycloalkyl alkyl in which the cycloakyl may optionally be substituted or a group of the formula ##STR1## wherein R.sup.1, R.sup.2 and R.sup.3 can be the same or different and can be hydrogen, alkyl, alkoxy, halo, phenyl, substituted phenyl, or hydroxy; A can be sulfur, oxygen, or --CH.sub.2 --; and Alk is straight or branched chain alkylene; which comprises reacting an alcohol of the formula EQU R--OH
wherein R is defined as above, with a suitable base in an aprotic organic solvent to generate an alkoxide anion, removal of the organic solvent, and coupling of the alkoxide anion with a salt of a monohaloacetic acid in an aprotic polar solvent such as dimethyl sulfoxide (DMSO) to give the acid salt which can optionally be reacted with acid to give the .alpha.-alkoxy acetic acid product.
This process has the advantages of providing a high yield of product and being able to be conducted in one pot thus providing a guicker, more efficient and less costly synthesis. The process of the present invention permits the unexpectedly efficient and convenient preparat of .alpha.-alkoxy acetic acids in improved overall yield and purity and is especially useful for preparing phenylthio-.alpha.-alkoxy acetic acids.
(b) Prior Art
U.S. Pat. No. 4,711,903 and U.S. Pat. No. 4,755,524 disclose a method of preparing a [2-[[3,5-bis(1,1 dimethylethyl)-4 hydroxyphenyl]thio]alkoxy]acetic acid from a 2,6-bis (1,1-dimethylethyl)-4-[(2-hydroxyalkyl) thio]phenol by a process in which chloroacetic acid is added to the alcohol in t-butyl alcohol which is a protic solvent, then potassium tert-butoxide is added, and the mixture is refluxed. This method gives yields of less than 25% and thus is not a very efficient process.
U.S Pat. No. 4,804,777 discloses a process for the preparation of an aryloxy acetic acid by oxidation of an aryloxyethanol in an agueous alkaline reaction medium at a temperature in the range of 0.degree. C. to the boiling point of the reaction medium in the presence of a catalytic amount of a catalyst comprised of palladium, silver, and optionally antimony, and carbon to form the corresponding alkali metal ester and contacting the alkali metal with a mineral acid.
U.S. Pat. No. 3,918,899 discloses a method of preparing carboxymethylated cottons in non-aqueous media by reacting anhydrous sodium cellulosate with a salt of a monochloroacetate in an anhydrous DMSO solution. R. C. Fuson and B. H. Wojcik, ORGANIC SYNTHESIS COLLECTED VOLUMES, 2:260-262(1943) discloses a three-step method for preparing ethoxyacetic acid from ethanol which is the substrate and the solvent (protic solvent).